Guide to Epidural Anesthesia: For Labor and in Surgery
Epidural anesthesia, best known for its role in alleviating labor pains, provides surgical and post-surgical pain relief for other procedures as well.
Epidurals are sometimes used in hip and knee surgery and to control pain after abdominal procedures. Most commonly though, epidural anesthesia is used during labor, at the request of the patient, to ease labor and delivery.
What is an Epidural? How Does Epidural Anesthesia Work?
The word epidural means "over or around the dura". The dura is the tough fibrous lining that surrounds the spinal cord and spinal fluid. The epidural space is the space outside or around the dura then.
The epidural space contains blood vessels such as the epidural veins, fat and spinal nerve roots. Outside of the epidural space sit the ligaments and finally the bones of your spinal column.
Epidural anesthesia takes advantage of the fact that there are nerve roots in the epidural space. A special needle is used to locate the epidural space and a small catheter (like IV tubing but thinner) is left in the space and the needle is removed. Medicine can be infused into this tubing to keep the nerve roots numb for surgery, labor or pain relief after a procedure.
How is an Epidural Placed?
Anesthesiologists and nurse anesthetists are the only clinicians placing epidural anesthesia. Epidural injections for back pain are done by pain specialists (anesthesiologists who specialize in pain management) and sometimes by specially trained radiologists and spine specialists.
Position: For placement of an epidural, you will either sit or lay on your side. Either way, it will be important that you curl up and don't arch your back. You want to push the low part of your back toward the anesthesiologist, like a "mad cat" or a shrimp, in a "C" shape. This is important to the success of the block since you must open up the spaces between the bones for access to the epidural space.
Procedure: The anesthesia provider will clean your back of with sterilizing solution. Then, they will tell you that you will feel a pinch. This is numbing medicine injected to numb the skin and structures under the skin to make the rest of the procedure more comfortable for you.
You then will be told to hold still. You should breathe evenly, even through contractions if you are getting a labor epidural. The anesthesiologist is using a special hollow needle to find the epidural space. This should feel like they are pushing on your back with a pencil eraser or their finger.
This part can go slow because it's not always easy to find the epidural space. If you move or have contractions, your anesthesiologist may wait for you to be still or the contraction to pass. When the anesthesia provider feels the needle pass into the ligament, they attach a syringe of saline to the end of the hollow needle. The needle is advanced very, very slowly. When the needle is still in the ligament and pressure is applied to the syringe with saline, resistance is felt. When the needle exits the ligament and enters the epidural space, there is a "loss of resistance" and resistance to pushing on the syringe suddenly "gives", and the saline is injected into the epidural space.
The syringe is removed from the needle. A small catheter is placed through the hollow needle and into the epidural space. The needle can be removed over the catheter which is left in place. So, at the end, the needle is out and the catheter is in.
Medicine is now injected into the catheter and pain relief is on the way!
Complications of Epidural Anesthesia
Every medical procedure has potential side effects and complications.
Failure: The biggest risk of the epidural is failure. The epidural can fail completely or partially. More commonly, the epidural anesthesia works, but perhaps only on one side or in a patchy distribution. Sometimes this has to do with the path the catheter takes in the epidural space and can sometimes be improved if the anesthesiologist pulls the catheter back a bit. Sometimes, there are barriers like strands of connective tissue or scar in the epidural space that keeps the epidural medicine from spreading and numbing all of the nerve roots. There is no way to predict who will have complete anesthesia and who will have patchy anesthesia. If the epidural anesthetic doesn't spread well to give good pain relief, this is disappointing for the patient and the doctor.
Bleeding: Because there are blood vessels in the epidural space, bleeding is a risk. Usually, if one of these blood vessels bleeds, it clots off easily and doesn't cause a problem. However, if you are on blood-thinners, or rarely as a random event, the blood vessel doesn't clot off. This becomes a medical emergency because if the bleeding isn't stopped, a hematoma (collection of blood) can form in the epidural space. The hematoma compresses the spinal cord and permanent paralysis can result if the hematoma isn't diagnosed (usually with MRI) and surgically relieved within a few hours. Pregnant women have bigger and more blood vessels in the epidural space, so if you are pregnant and on blood thinners, you will most likely not be able to have an epidural for labor.
Luckily, this complication is extremely rare, with an incidence of only about 1 in 150,000 to 190,000 epidural anesthetics, as reported in a review of the literature published in the journal "Anesthesia and Analgesia" in 2002. That was seven hematomas in 1.3 million epidurals.
Infection: Anytime a needle or medical instrument passes from the outside environment, through the skin to an internal space like the epidural space, infection is a risk. People who are taking drugs (like chemotherapy or drugs for autoimmune diseases) that suppress their immune systems are at increased risk. The incidence for this epidural complication is about 1 in 2000. Treatment is with antibiotics and possibly surgical drainage.
Nerve Damage: The incidence of nerve damage attributable to epidural analgesia and anesthesia is harder to compute. Labor epidurals usually are only in place for a few hours and then are removed. While it's possible that the catheter or medicine can irritate the nerve roots and cause lasting numbness or weakness, it doesn't seem to be very common.
If you have a lumbar epidural for labor and have numbness or weakness afterwards, it's possible that the nerve problem is from labor itself. The delivery position used in the United States of putting the legs in stirrups and then flexing from the hips, can damage several nerves. This is actually quite common. Most often, numbness over the front of the thigh and "foot drop" are from this positioning. Also, pressure from the baby's head on the pelvic brim causes certain kinds of nerve injury.
Regardless of cause, these nerve deficits are usually temporary and resolve on their own or with physical therapy in more significant cases. There are muscle and nerve tests that can be done to help figure out the origin of the nerve injury if that becomes important.
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